Elements of Theology, Proposition 11

ON CAUSE

All beings proceed from One First Cause.
 

For either there is no cause of any being, or the causes of all finite things revolve in a circle, or the as­cent (progression) is to infinity, and one thing is the cause of another, and the presubsistence of essence (cause) will in no respect cease. If, however, there is no cause of beings, there will be neither an order of things second and first, of things perfecting and perfec­ted, of things adorning and adorned, of things generat­ing and generated, and of agents and patients, nor will there be any science of beings. For the knowledge of causes is the work of science, and we are then said to know scientifically when we know the causes of things. But if causes revolve in a circle, the same things will be prior and posterior, more powerful and more imbecile. For every thing which produces is better than the nature of that which is produced. Nor does it make a differ­ence to conjoin cause to effect, and through many or [11] fewer media to produce from cause. For cause will be superior to all the intermediate natures of which it is the cause; and the more numerous the media the greater is the causality of the cause.

 

And if the addition of causes is to infinity, and there is always again a cause prior to another, there will be no science of any being: for there is not a knowledge of any thing infinite. But causes being unknown, neither will there be a science of the things consequent to the causes. If, therefore, it is necessary that there should be a cause of beings, and causes are distinct from the things caused, and there is not an ascent to infinity, there is a First Cause of beings, from which as from a root every thing proceeds,—some things indeed being nearer to but others more remote from it. The neces­sity of the existence of One Principle has been demon­strated, because all multitude is secondary to The One.

COMMENTARY

This one seems straightforward enough. There is one cause of all things; this is Platonism 101. Either things are caused or they are not. If they are not, it's not clear how they could exist at all. If they are, then there is either one first cause, or causality is circular, or causality proceeds to infinity. It's interesting to note that Proclus argues from the "science" of causality to demonstrate its existence. That itself is an important tidbit which I believe we should keep in our minds as we proceed. 

Why could there not be two first causes of all things? If there were, then either they or the things they cause relate to one another or do not relate to one another. If they do not relate to one another, then we're left with an absurdity, because we will have two separate sets of "all things" which have no possibility of any contact with one another. But this is impossible, because if both sets consist of "all things" then, at minimum, they share something, which is existence. But if there are two first causes which do relate to one another, at least by way of existence, then neither can be the first cause, because they are united by a third thing. That third thing, in turn, must actually be prior to them, because if it is not prior, they will not both be able to share it. Therefore the shared substance of both will be the First Cause. 

Therefore there is a First Cause, "a root from which all things proceed," and this is nothing other than the One Itself.